Sliding doors are known, which comprise a load-bearing frame connected to a masonry or partition wall of a building and adapted to support a sliding door shutter between a closed position and an open position.
Sliding doors also typically include a sliding support system for supporting the shutter, which comprises one or more carriages fixed to the upper and/or lower edges of the shutter, each equipped with one or more pairs of wheels sliding within a guide associated with the load-bearing frame.
The shutter may be opened/closed by simply acting thereupon with a sufficient force to cause the carriages to slide along the guide
Nevertheless, if large shutters are used, the user will be required to exert a very large force to promote movement thereof.
This may cause difficulties in using the door by particular classes of people such as children, the elderly or the handicapped.
Furthermore, the difficulty in opening/closing large sliding doors may be a risk in emergencies.
In order to ensure both easy access by any kind of user and safety, the force that the user is required to apply on the shutter to promote sliding thereof shall not exceed a predetermined value, which is established by applicable standards.
Therefore, sliding doors are known which comprise shutter supporting systems adapted to relieve the weight thereof and reduce the effort required of the user below such reference values.
U.S. Pat. No. 7,752,810 discloses a sliding door supporting device which comprises a guide fixed to the upper edge of the frame, for slidingly receiving a carriage that is adapted to support a door shutter by appropriate connection means.
The carriage comprises a pair of wheels sliding on the guide and an upper wall for supporting a plurality of first magnets having the same magnetic polarity. The guide has a seat for housing a plurality of second magnets in facing relationship to the first magnets and with opposite polarity.
The first magnets integral with the carriage and the second magnets integral with the guide have an air gap therebetween with the flux lines of the magnetic field passing therethrough to exert an upward attractive force on the carriage and counteract the weight force of the sliding shutter.
A first drawback of this known arrangement is that the carriage has a great thickness and the edge of the door shutter connected thereto projects out of the guide, whereby the system is very bulky.
Furthermore, the great distance between the carriage and the shutter edge facilitates horizontal oscillations of the shutter in response to the force applied by the user, which will reduce slidability of the shutter as it is being opened or closed.
The considerable bulk of the support system complicates installation in an adequate mounting space, which makes the system unsuitable for small-size installation conditions.
A further drawback of this prior art system is that the fixation arrangement that secures the door shutter outside the guide is externally visible, and reduces aesthetic quality, by affecting visual cleanness of the door.
Another serious drawback of this arrangement is that the air gap between the first and second magnets is not easily adjusted, as its adjustment requires operation of screw means that are hardly reachable, as they are entirely embedded in the guide.